U.S. patent number 11,391,550 [Application Number 16/868,734] was granted by the patent office on 2022-07-19 for cook-off mitigation systems.
This patent grant is currently assigned to The United States of America, as represented by the Secretary of the Navy. The grantee listed for this patent is The United States of America, as represented by the Secretary of the Navy, The United States of America, as represented by the Secretary of the Navy. Invention is credited to Que T. BuiDang, Donald L. Burnett, Josiah S. Garfield, Lee R. Hardt, Robert A. Koontz, Eric K. Wooding.
United States Patent |
11,391,550 |
Hardt , et al. |
July 19, 2022 |
Cook-off mitigation systems
Abstract
The disclosed embodiments are directed to enhancing insensitive
munitions performance. Some of the embodiments employ an outgassing
pad having unique geometrical configurations, compositions, and
positioning. Other embodiments rely on using thermally-releasable
components to foster billet expulsion. Additional embodiments
combine both aspects into entire cook-off mitigation systems for
insensitive munitions improvements.
Inventors: |
Hardt; Lee R. (Ridgecrest,
CA), Burnett; Donald L. (Spearfish, SD), Garfield; Josiah
S. (Ridgecrest, CA), Koontz; Robert A. (Anchorage,
AK), Wooding; Eric K. (Ridgecrest, CA), BuiDang; Que
T. (Ridgecrest, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
The United States of America, as represented by the Secretary of
the Navy |
Arlington |
VA |
US |
|
|
Assignee: |
The United States of America, as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
1000004812861 |
Appl.
No.: |
16/868,734 |
Filed: |
May 7, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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16113786 |
Aug 27, 2018 |
10724836 |
|
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|
15380679 |
Oct 16, 2018 |
10101139 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F42B
39/20 (20130101); F42B 12/207 (20130101); F42B
39/14 (20130101); F42B 12/20 (20130101); F42C
19/02 (20130101); F41A 17/16 (20130101) |
Current International
Class: |
F42B
12/20 (20060101); F42B 39/14 (20060101); F42B
39/20 (20060101); F42B 12/14 (20060101); F41A
17/16 (20060101); F42C 19/02 (20060101) |
Field of
Search: |
;102/481 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bergin; James S
Attorney, Agent or Firm: Naval Air Warfare Center Weapons
Division Saunders; James M.
Government Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
The invention described herein may be manufactured and used by or
for the government of the United States of America for governmental
purposes without the payment of any royalties thereon or therefor.
Claims
What is claimed is:
1. A cook-off mitigation system, comprising: a munition having a
munition casing, an interior compartment, a nose end, and a tail
end; an explosive fill housed in said interior compartment; a fuze
well attached to said tail end of said munition casing; a fuze
housed inside said fuze well; and a charging well housed entirely
in said munition casing, wherein a munition protective liner
separates said charging well from said explosive fill, said
charging well, further comprising: a charging well cavity
penetrating said munition casing, said charging well cavity having
a proximal end, a distal end, and a threaded interior surface; a
charging well component having a threaded exterior surface, wherein
said charging well component is attached inside said charging well
cavity by threading engagement of said threaded interior surface
and said threaded exterior surface; wherein said charging well
component is in electrical communication with said fuze by a
communication conduit; and a eutectic charging tube extension
having a first end and a second end, wherein said first end is
configured for mating engagement with said charging well component,
wherein said second end is configured for mating engagement with
said communication conduit.
2. The system according to claim 1, further comprising a cutter
device positioned adjacent to said eutectic charging tube extension
and attached to said charging well component.
Description
FIELD
The embodiments generally relate to insensitive munitions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of an outgassing pad, according to some
embodiments.
FIG. 2A is a section view of an outgassing pad with a shell,
according to some embodiments.
FIG. 2B is a section view of an outgassing pad without a shell,
according to some embodiments.
FIG. 3A is a nose end perspective view of the outgassing pad in
FIG. 1, according to some embodiments.
FIG. 3B is a tail end perspective view of the outgassing pad in
FIG. 1, according to some embodiments.
FIG. 4 a close-up of a partial section view of a charging well,
according to some embodiments.
FIG. 5 is a partial section view of a cook-off mitigation system in
a generic munition, according to some.
FIG. 5A is a partial cutaway section view of the tail end of the
system in FIG. 5, according to some embodiments.
FIG. 6 is an exemplary exploded view of a eutectic device that can
be used in some embodiments.
FIG. 7 is a close-up partial section view of a gas sealing device
shown in its operating environment.
FIG. 8 is an inverted isometric view of some components in the
charging well from FIG. 4.
It is to be understood that the foregoing general description and
the following detailed description are exemplary and explanatory
only and are not to be viewed as being restrictive of the
embodiments, as claimed. Further advantages of the embodiments will
be apparent after a review of the following detailed description of
the disclosed embodiments, which are illustrated schematically in
the accompanying drawings and claims.
DETAILED DESCRIPTION OF EMBODIMENTS
Embodiments may be understood more readily by reference in the
following detailed description taking in connection with the
accompanying figures and examples. It is understood that
embodiments are not limited to the specific devices, methods,
conditions or parameters described and/or shown herein, and that
the terminology used herein is for the purpose of describing
particular embodiments by way of example only and is not intended
to be limiting of the claimed embodiments. Also, as used in the
specification and appended claims, the singular forms "a," "an,"
and "the" include the plural.
Embodiments generally relate to insensitive munitions (IM)
improvements, especially with respect to cook-off mitigation
systems. Some embodiments employ an outgassing pad in the nose of
the munition. Additional embodiments employ a releasable (two-part)
charging well. Further embodiments combine these approaches with a
releasable tail closure mechanism.
Although the embodiments are described in considerable detail,
including references to certain versions thereof, other versions
are possible. Examples of other versions include orienting and/or
attaching components in different fashion. Therefore, the spirit
and scope of the appended claims should not be limited to the
description of versions included herein.
Components and Materials Used
In the accompanying drawings, like reference numbers indicate like
elements. Reference characters 100, 400, and 500 are used to depict
various embodiments. Several views are presented to depict some,
though not all, of the possible orientations of the embodiments.
Some figures depict section views and, in some instances, partial
section views for ease of viewing. The patterning of the section
hatching is for illustrative purposes only to aid in viewing and
should not be construed as being limiting or directed to a
particular material or materials. Unless stated otherwise,
components depicted are dimensioned to be close-fitting and to
maintain structural integrity both during storage and while in
use.
Components used in several embodiments, along with their respective
reference characters, are depicted in the drawings. Reference
character 100 depicts an outgassing pad. In some embodiments, the
outgassing pad 100 includes a shell 102 and an outgassing agent
104, such as a powder and binder mix. The shell 102 can be an
elastomeric shell such as silicone, rubber, or silicone-rubber. The
outgassing agent 104 is a powder and binder mix. The elastomeric
shell 102, may also be referred to as an outgassing shell,
container, or bladder, and can be used to house the outgassing
agent 104 as a technique for controlled fragmentation, enhanced gas
containment, and as a reduction in compatibility concerns. A person
having ordinary skill in the art will recognize the term
compatibility concerns to be synonymous with assuring that
chemicals coming in contact with an explosive fill are chemically
compatible.
In other embodiments, the shell 102 can be a non-elastomeric shell
such as plastic. In yet other embodiments, the shell 102 can be
eliminated. In embodiments without a shell 102, the outgassing pad
100 is the outgassing agent 104, as discussed further below. The
surface contours of the outgassing pad (reference character 100)
with a shell (reference character 102) as well as the outgassing
pad without the shell are the same. Section views best illustrate
the outgassing pad 100 embodiments. Generically, the outgassing pad
is depicted with reference character 100. Reference character 100A
depicts the section view of an outgassing pad with a shell, as
shown in FIG. 2A. The embodiment in FIG. 2A can also be referred to
as a confined or canistered outgassing pad 100A. Conversely, as
shown in FIG. 2B, reference character 100B depicts the section view
of an outgassing pad without a shell, and can be referred to as an
unconfined or uncanistered outgassing pad.
The shell 102 has unique geometrical configurations, including
surface contours having a sigmoid shape, ogee shape, or a cyma
recta shape. A person having ordinary skill in the art will
recognize that ogee and cyma recta are understood to be types of
sigmoid shapes. A person having ordinary skill in the art will
recognize that a sigmoid shape is a shape similar to the letter S.
Likewise, a person having ordinary skill in the art will recognize
that an ogee shape is descriptive of an S-shape and, moreover, is
characteristic of two curves meeting at a point. Additionally, a
person having ordinary skill in the art will recognize that a cyma
recta shape is descriptive of double curvature, combining both
convex and concave features. A person having ordinary skill in the
art will also recognize, after viewing FIG. 2A, that the shell 102
can have a first portion 210A that is characteristic of a rounded
trapezoid, truncated ogive or truncated ogival shape, and a second
portion 212A that is sigmoid-shaped, ogee-shaped, or cyma
recta-shaped. Likewise, the first portion 210A can also have a
meplat shape. A person having ordinary skill in the art will
recognize that the word meplat is used in ballistics and is a
technical term for a flat or open tip on the nose of a bullet. The
selected shapes are based on reducing stress concentration during
obturation and also shock wave focusing during target
penetration.
Likewise, the surface contour shapes are also applicable to the
embodiment depicted in FIG. 2B by reference characters 100B, 210B,
and 212B. Specifically, the outgassing pad without the shell
(reference character 100B) can also have a first portion 210B that
is characteristic of a rounded trapezoid, or meplat, truncated
ogive, or truncated ogival-shape, and a second portion 212B that is
sigmoid-shaped, ogee-shaped, or cyma recta-shaped. The selected
shapes are based on reducing stress concentration during obturation
and also shock wave focusing during target penetration.
Selection of the outgassing agent 104 is based on several factors
including volume-to-mass ratio of decomposition products,
activation temperature, compatibility and stability, cost, material
availability, and environmental concerns. The outgassing agent 104
is a powder-binder mix. Suitable powders for the outgassing agent
104 include a blowing agent mixed with an activator. Suitable
blowing agents include oxydibenzenesulfonyl hydrazide (OBSH) or
azodicarbonamide (ADC), due to their cell structures. The blowing
agent is mixed with the activator to tune the decomposition
temperature and rate. In the embodiments, zinc oxide is a suitable
activator. Depending on application-specific requirements, other
activators can also be used. Additionally, in other embodiments, an
activator may not be needed depending on the blowing agent selected
or other system requirements. Suitable binders for the outgassing
agent 104 include wax, tar, or an energetic binder. Binder
formation includes melt cast methods for waxes, cast-curing from a
mold, and press-molding for the powder-binder mixes.
In the unconfined embodiment (100B in FIG. 2B), the outgassing pad
100 is an outgassing agent 104 held in a specific geometry by
incorporating a binder. Thus, in some embodiments, the elastomeric
shell 102 can be eliminated by mixing the outgassing agent's 104
powder (such as azodicarbonamide and zinc oxide) and an activator
such as zinc oxide with a binding agent such as, for example,
asphaltic hot mix or Epolene wax. The mixture allows for the
application of the outgassing agent (and hence the outgassing pad
100B) and binder to be applied directly to the wall of the munition
502 as a liner.
The powders in the outgassing agents 104 will compact appreciably
during target penetration, which is undesirable. Adding the binder
to create a powder-binder mix eliminates this concern because the
binder fills the void spaces between the particles of the powder
which constitutes the powder, thus reducing the compaction. The
mixture of the powder-binder is determined based on
application-specific conditions. In some embodiments, the powder
(azodicarbonamide and zinc oxide) is a range of about 66 to about
68 percent and the binder is 30 percent. The variation in
constituents is from varying percentages of additive(s) used to
tune the peak exothermal temperature.
Instances having different ranges are also possible and can be
dependent on the processing of the material such as particle size,
particle geometry, packing fraction, and wettability. Additionally,
the cost of manufacturing/processing the material can drive one
process over another which can correspondingly change the requisite
ranges. Based on this, in other embodiments, the range is about 60
percent to about 70 percent powder, and a binder range of about 30
to about 40 percent, with the remaining constituents being
additive(s) used to tune the peak exothermal temperature. Likewise,
when tuning the powder-binder mix to expel a munition's explosive
billet, the unique characteristics of that specific munition can
drive the percentages. As such, a larger/different range can be
beneficial in addressing the maintaining of the mass properties of
a munition system by adjusting the powder-binder mixture to closely
match the density of the munition's main explosive billet, thus
avoiding changes to flight or performance characteristics.
Reference character 400 depicts a charging well that is housed
entirely in the munition casing 504, with no portion inside the
explosive fill. The charging well 400 employs a charging well
component 408, fasteners 414, a cutting device 415, sometimes
referred to as a cutter, knife blade or other variation, and a
eutectic charging tube extension 413. The charging well component
408 is generically depicted because the embodiments are applicable
to a variety of charging well components without detracting from
the merits or generalities of the embodiments. The charging well
component 408 is contoured to match the munition case 504 interior
contours, defined by a cavity 402 in the munition case 504.
Additionally, a person having ordinary skill in the art will
recognize the specific components used in charging wells. The
charging well component 408 is a structural material and, in most
embodiments, is steel. A protective liner 411 is shown in some
embodiments. Suitable liner materials include asphaltic hot melt,
wax coating, and plastic.
FIG. 5 depicts a cook-off mitigation system 500 in a generic
munition 502. In addition to the outgassing pad 100 and charging
well 400, the system 500 includes a munition casing 504 with an
interior wall 506 defining at least one interior compartment
configured to house an explosive fill 508. The interior wall 506 is
the interior surface of the munition casing 504. As such, reference
character 506 is used herein for both the interior wall and the
interior compartment since the interior wall defines the interior
compartment. At times the explosive fill 508 is referred to as an
explosive billet or simply as an explosive without detracting from
the merits or generalities of the embodiments. Steel conduit 518,
sometimes referred to as a charging tube, can be used to house
cable (not shown for ease of view) transmitting power and/or
signals between the charging well 400 and a steel fuze well 511.
References to the use of steel herein also include steel alloys. A
releasable tail closure mechanism 512 employs a base plug 514 and
releasable base plate 516.
Additional components are shown for orientation purposes and to
assist in understanding operating environments. In particular, FIG.
5 is very useful for illustrating an operating environment for
several of the features employed in the embodiments. A synthetic
felt pad 520 is generically shown and can be used in some munitions
to provide ullage space, but is not needed in all munitions.
Sealant 522 is also generically shown, and is used to prevent
slumping of the explosive billet 508 during curing in some, but not
all munitions. A steel fuze well retaining ring 524 assists in
securing the fuze well 511 to the munition casing 504. Eutectic
devices, such as eutectic retaining nuts and plates, are used and
are discussed in greater detail below.
Apparatus and System Embodiments
An outgassing pad for cook-off mitigation is depicted by reference
character 100 in FIGS. 1, 3A, 3B, & 5. The outgassing pad for
cook-off mitigation 100 is sometimes referred to simply as an
outgassing pad, pad, and the like, without detracting from the
merits or generalities of the embodiments. FIG. 1 is a side view of
the outgassing pad 100. FIG. 1 is generic with respect to its
application of an outgassing pad with a shell and an outgassing pad
without a shell and, thus, is generically depicted using reference
character 100. Specific section views of an outgassing pad with a
shell and an outgassing pad without a shell are depicted by
reference characters 100A & 100B in FIGS. 1A & 2B,
respectively. As such, FIG. 2A is the section view of the
outgassing pad with shell along cut plane 2A-2A in FIG. 1. FIG. 2B
is the section view of an outgassing pad without a shell along cut
plane 2B-2B in FIG. 1. FIGS. 3A & 3B show the outgassing pad
100 from nose end and tail end perspective views, respectively.
FIG. 4 is a close-up partial section view of a charging well for
cook-off mitigation, as depicted by reference character 400. FIG. 8
is an inverted isometric view of some components and their
associated structural features in the charging well 400. The
charging well for cook-off mitigation 400 is sometimes referred to
simply as a charging well and other similar variations, without
detracting from the merits or generalities of the embodiments. FIG.
5 illustrates a cook-off mitigation system 500 in a generic
munition 502. FIG. 6 is an exploded view of a eutectic device 600
that can be used in some embodiments. FIG. 7 is an exploded view of
a gas sealing system 700 that may be used in some embodiments.
Referring to FIG. 2A, the outgassing pad with a shell (reference
characters 100A and 102) houses an outgassing agent 104. Referring
to FIGS. 1 & 5, a generic munition is depicted with reference
character 502 having a munition casing 504 with an interior wall
506. The munition 502 has a nose end 503 and a tail end 505. The
interior wall 506 defines an interior compartment that is
configured to house an explosive fill 508. The outgassing pad 100
is positioned inside the interior compartment 506 and adjacent to
the interior nose end 510 of the munition 502.
Outgassing pad 100 positioning and, therefore, the shell 102, such
as in the embodiment depicted in FIG. 2A by reference character
100A, is notable because previous attempts at using an outgassing
pad were, if employed at all, positioned in an aft vent and not in
the nose end. Similarly, the embodiment depicted in FIG. 2B by
reference character 100B is also notable for the same reason.
Furthermore, previous attempts at using outgassing pads, if used at
all, were flat, circular discs and not shaped as disclosed
herein.
The shell 102 has at least two sides 210A & 212A, synonymous
with the first and second portions mentioned above, that are
diametrically-opposed to each other with one of the two sides being
adjacent to the interior nose end 510 of the munition 502. Viewing
FIGS. 2A & 5 simultaneously, it is readily apparent that the
side depicted by reference character 210A is adjacent to the
interior nose end 510 of the munition 502. The other side, depicted
by reference character 212A, is adjacent to the explosive fill 508
housed in the interior compartment 506 of the munition 502. The
explosive fill 508 holds the shell 102 adjacent to the interior
nose end 510. Adhesive can be used, if desired, to adhere the shell
102 adjacent to the interior nose end 510.
Similarly, the outgassing pad without a shell (reference character
100B in FIG. 2B) also has at least two sides 210B & 212B,
synonymous with the first and second portions mentioned above, that
are diametrically-opposed to each another with one of the two sides
being adjacent to the interior nose end 510 of the munition 502.
Viewing FIGS. 2B & 5 simultaneously, it is readily apparent
that the side depicted by reference character 210B is adjacent to
the interior nose end 510 of the munition 502. The other side,
depicted by reference character 212B, is adjacent to the explosive
fill 508 housed in the interior compartment 506 of the munition
502. The explosive fill 508 holds the outgassing pad without a
shell (reference character 100B) adjacent to the interior nose end
510. Adhesive can be used, if desired, to adhere the outgassing pad
without a shell (reference character 100B) adjacent to the interior
nose end 510. Additionally, the outgassing pad without a shell
(reference character 100B) can be adhered to the interior wall 506
of the munition by selecting a binding agent such as, for example,
asphaltic hot mix or Epolene wax, which allows for the application
of the outgassing agent and binder to be applied directly to the
interior wall of the munition 502 as a liner.
Referring to FIG. 4, the components in the charging well 400 are
shown assembled. The charging well 400 includes a charging well
cavity 402 that is a void that penetrates the munition casing 504.
The charging well cavity 402 has a proximal end 404, a distal end
406, and threaded surface, sometimes referred to as a threaded
interior surface (not shown for ease of viewing). A counterbore
403, sometimes referred to as a spot face, transitions to the
proximal end 404 of the cavity 402 and is configured as shown to
create a smooth, flat surface to assist with mating.
Referring to both FIGS. 4 & 8, the charging well component 408
has a threaded exterior surface 802. The charging well component
408 is attached inside the charging well cavity 402 by threading
engagement of the charging well component's threaded exterior
surface 802 to the threaded interior surface of the charging well
cavity. Stated another way, the threaded exterior surface 802 can
be referred to as mating threads that attach the charging well
component 408 to the munition casing 504, i.e. inside the charging
well cavity 402. Both the charging well cavity 402 and charging
well component 408 have appropriate thread relief features.
Referring to FIGS. 4 & 5, the munition casing 504 has a nose
end 503 and a tail end 505. The charging well component 408 is
electrically connected, sometimes referred to as in electrical
communication with, a munition fuze 513 via the conduit 518, which
can be referred to as a communication conduit and/or power cable
conduit. The munition fuze 513 is housed in a fuze well 511 at the
tail end 505. A eutectic charge tube extension 413 has a first end
416 and a second end 418. The first end 416 of the eutectic charge
tube extension 413 is configured for mating engagement with the
charging well component 408. The second end 418 is configured for
mating engagement with the communication conduit 518 (the opposing
end of the communication conduit--opposite from the end connected
to the fuze well 511/fuze 513.
An explosive fill 508 is generically shown in FIG. 5 and is housed
in the munition casing 504. The munition casing 504 is steel and
has an interior protective liner 411 separating the munition casing
and the charging well 400 and, hence, the charging well cavity 402
and charging well component 408 from the explosive fill 508.
The cutter/cutting device 415 is positioned adjacent to the
eutectic charge tube extension 413 and is attached to the charging
well component 408 by fasteners 414. Other attachment methods can
be used including adhesives. The eutectic melt temperature of the
eutectic charging tube extension 413 is less than the outgassing
temperature of the outgassing agent. The cutter/cutting device 415
is held in a fixed position and is configured to cut the cable(s)
inside the conduit 518 and eutectic charge tube extension 413 after
the eutectic charge tube extension has melted during a cook-off
event. This prevents the cable(s), conduit 518, and any portion of
the eutectic charging tube extension 413 remaining to move toward
the tail end 505.
Void spaces 420A & 420B are shown in FIG. 4. The void spaces
420A & 420B are shown for attachment with communication plugs
(not shown for ease of viewing) to transfer power or information
via the void spaces through the eutectic charging tube extension
413, communication conduit 518, and finally to the munition fuze
513. Thus, the charging well component 408 is a communication
interface between communication plug(s) and the fuze 513. A cutter
device void space 422 exposes the cutting device 415 internally in
the charging well component 408 for efficient cutting.
FIGS. 5 & 5A depict another embodiment. A cook-off mitigation
system 500 in a generic munition 502 is shown. In particular, the
system 500 includes the outgassing pad 100, the charging well 400
and associated components discussed previously. The charging well
400 and associated components are electrically-connected to the
fuze well 511 to provide power to a munition fuze 513 that is
housed in the fuze well, and shown generically for ease of viewing.
As depicted in FIG. 5, the charging well 400 is located
(positioned) at about the midpoint (middle) of the munition 502,
which is about half way between the nose end 503 and tail end 505.
As discussed above, mating threads attach the charging well 400 and
associated components to the munition casing 504. A releasable tail
closure mechanism 512 (depicted in FIG. 5A) is attached to the tail
end 505 of the munition casing 504 and is configured to house an
explosive fill 508 in the interior compartment 506.
FIG. 5A is a partial cutaway section view of the tail end 505 of
the system 500 in FIG. 5. The releasable tail closure mechanism 512
has a base plug 514 that is concentric about the fuze well 511 and
is attached to the munition casing 504. The base plug 514 is steel
or steel alloy. A thermally-releasable base plate 516 is concentric
about the fuze well 511 and fits on the outer periphery of the base
plug 514 and is attached to the base plug and the munition casing
504. As shown in FIG. 5A, the releasable tail closure mechanism 512
includes both the base plug 514 and the thermally-releasable base
plate 516. In some embodiments, the thermally-releasable base plate
516 is a eutectic device. However, the method the base plate 516
uses to release does not have to be only eutectic as long as it
releases prior to the outgassing of the material. Thus, alternative
materials include a shape memory alloy or a polymeric material.
Components depicted are dimensioned to be close-fitting and to
maintain structural integrity both during storage and while in
use.
FIG. 6 illustrates a eutectic device, generically depicted with
reference character 600, which can be used in some embodiments,
including the thermally-releasable base plate 516 shown in FIG. 5A.
The eutectic feature in FIG. 6 is based on U.S. Air Force venting
configurations. The eutectic device 600 is shown in an exploded
view and is representative of the eutectic device 516 shown in FIG.
5A, respectively. The eutectic device 600 includes a hub ring 602
having a proximal side 604 and a distal side 606. The distal side
606 has a plurality of threaded recesses 608. Suitable materials
for the hub ring 602 include steel and steel alloys. A eutectic
ring 610 has an inner surface 612, an outer surface 614, and a rib
616 on its outer surface. The inner surface 612 of the eutectic
ring 610 is concentric about the hub ring 602. Suitable materials
for the eutectic ring 610 include metal alloys having about 58
percent bismuth (Bi) and about 42 percent tin (Sn). The eutectic
ring 610 composition is tuned to a desired aft closure release
temperature. Adjusting the percentages may change the melt
temperature, which may allow for tuning of the desired release.
Thus, in some embodiments, the bismuth (Bi) composition may be
about 50 to 60 percent and the tin (Sn) composition is about 40 to
50 percent, depending on the desired release temperature.
A spring ring 618 is concentric about the eutectic ring 610. The
spring ring 618 has a slot 620 that is dimensioned to engage the
rib 616 on the eutectic ring 610. Suitable materials for the spring
ring 618 include steel and spring back steel. The rib 616 and slot
620 engagement prevents axial movement of the spring ring 618 about
the eutectic ring 610. A retainer ring 622 has a plurality of
apertures 624 that are thru-holes in the retainer ring. Suitable
materials for the retainer ring 622 include steel. When assembled,
the retainer ring 622 is abutted against the hub ring 602, the
eutectic ring 610, and the spring ring 618. A plurality of screws
626 fasten the retainer ring 622, the spring ring 618, the eutectic
ring 610, and the hub ring 602 together by being inserted through
the plurality of apertures 624, through the retainer ring 622, and
into the plurality of threaded recesses 608 on the distal side 606
of the hub ring 602. The screws 626 can be steel or steel alloy cap
screws.
FIG. 7 depicts a gas sealing device 700, sometimes referred to as a
sealing device or mechanism. The sealing device 700 is co-extensive
with a portion of the protective liner 411. The sealing device 700
has a steel O-ring holder 701 configured to hold an O-ring 702.
Rubber is an appropriate material. More accurately, a high
temperature rubber material is selected, such as silicone or a
fluoropolymer elastomer rubber. The O-ring holder 702 may be
positioned at the forward end of the full internal diameter of the
munition casing 504.
Theory of Operation
Outgassing pad 100 positioning in the interior nose end 510 in
conjunction with the defined geometry, described herein, aids in
containing decomposition products to more effectively control the
expulsion of explosive billet 508 out of the munition 502 after the
release of the tail closure mechanism 512 and charging tube
extension 413. Less outgassing agent 104 can be used and provides
for a more focused outgassing environment. Outgassing agent 104
quantity can change due to the quantity of gases needed to expel
the explosive billet 508. Positioning the outgassing pad 100 in the
nose end 503 of the munition 502 reduces the risk of shock
initiation of the explosive fill 508 in hard target penetration
munitions.
The outgassing pad 100 location, geometry, and outgassing agent 104
selection is based on the anticipated gaseous products and reaction
temperature for a specific munition. Employing an elastomeric shell
102 allows contained expansion and uniform pressure upon the
explosive billet 508 until the elastomeric shell ruptures.
Decomposition of the outgassing agent 104 occurs prior to reaction
of the explosive fill (at a temperature range of about 280 degrees
F. to about 320 degrees F. for some explosive fills and about 280
degrees F. to 350 degrees F. for other explosive fills).
The selected shape of the outgassing pad 100 is such that it
expands as a wedge and obturates the explosive fill 508. One having
ordinary skill in the art will recognize that obturate is a term
for sealing by expanding. Thus, the outgassing pad 100 expands as a
wedge and further expands the portion of the explosive billet 508
at the interior nose end 510 against the interior wall 506, further
sealing the expanding gas at rupture. Silicone is used for the
elastomeric shell 102 to allow for contained expansion at elevated
temperatures and uniform pressure upon the explosive billet 508
until the elastomeric shell ruptures.
To avoid possible detrimental fragmentation effects to the nose end
503 of the munition 502, the outgassing pad 100 and, especially the
elastomeric shell 102, can also contain fragmentation control
patterns to contour the explosive charge and influence preferential
fragmentation. With the internal pressure created by the outgassing
agent 104, the explosive billet 508 can be expelled from the
munition 502 using the releasable tail closure mechanism 512 prior
to ignition of the explosive billet. Thermal release of the
eutectic devices occurs at a range of about 280 degrees F. to about
320 degrees F. This allows the explosive billet 508 to burn totally
unconfined, thus producing a passing reaction by reducing the
severity of the munition reaction to standardized IM cook-off
testing, often referred to as slow cook-off (SCO) and fast cook-off
(FCO). The cook-off temperatures are greater than the munition's
operational temperatures. One skilled in the art will recognize
that insensitive munitions testing includes identifying the
system's response to standardized testing. Munitions responses are
assessed depending on multiple variables and an acceptable
reaction, sometimes referred to as a passing reaction or passing
test.
The charging well 400 is configured to remain functional at
operational temperatures but weaken at cook-off temperatures,
allowing for the unimpeded expulsion of the explosive billet 508.
The eutectic charge tube extension 413 is a eutectic material, that
maintains structural integrity of the eutectic charge tube
extension during operation through munition 502 impact, but will
soften and/or melt before the outgassing pad 100 outgasses. The
eutectic charge tube extension 413 in one embodiment is bismuth,
tin, and indium. In other embodiments, the charge tube extension
413 does not have to be eutectic provided that it softens at a high
temperature, such as a polymer. The cutting device 415 will cut the
eutectic charge tube extension 413 (if needed) and cables (not
shown) in the conduit 518 as the explosive billet 508 is pushed
toward the tail end 505 of the munition case 504 when the
outgassing pad 100 outgases. Additionally, the entire charging well
cavity 402 and component 408 is outside of the explosive billet
508, as shown in FIG. 4. Thus, lateral movement of the explosive
billet is not to be limited by the charging well 400, communication
conduit 518, or eutectic charging tube extension 413. Once the
eutectic charge tube extension 413 is thermally released or
severed, the conduit 518 is concurrently released, while the
explosive billet 508 is moving laterally from the nose end 503
through the tail end 505, as the thermally-releasable base plate
516 releases.
In an embodiment employing an unconfined/uncanistered outgassing
pad 100B, as depicted in FIG. 2B, the outgassing pad is in direct
contact with the explosive billet 508. The outgassing pad 100B is
selected to be chemically compatible with the explosive billet 508.
As with the embodiment employing a shell 102, the
unconfined/uncanistered outgassing pad 100B generates gas. The
generated gas is applied to the explosive billet 508 and the
release process described above occurs and the explosive billet is
expelled.
The sealing device 700 can be used to reduce leakage of gas and to
push the explosive billet 508. A steel ring holder 701 with O-Ring
702 pushed all the way to the forward transition between the full
inside diameter and ogive of the munition case 504 before the
protective liner 411 is applied. The location of the sealing device
700 is at the transition of the interior wall 506 from being
straight (having a constant internal diameter) to the portion of
the interior wall having a tapered internal diameter due to the
ogive shape of the munition 502. The sealing device 700 is as an
extra safety measure in case the outgassing pad 100 does not expand
as a wedge. In those instances, the sealing device 700 will
obturate and influence the explosive billet 508 to move to the tail
end 505 during cookoff events.
While the embodiments have been described, disclosed, illustrated
and shown in various terms of certain embodiments or modifications
which it has presumed in practice, the scope of the embodiments is
not intended to be, nor should it be deemed to be, limited thereby
and such other modifications or embodiments as may be suggested by
the teachings herein are particularly reserved especially as they
fall within the breadth and scope of the claims here appended.
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